Preparation Of Modifide BiVO₄and Its Photo-catalytic Performance

In recent years, the study of using photocatalytic technology for the degradation of organic pollutants in the waste water and air has been active. It is necessary to develop new photocatalytic with high visible light response ability to substitute TiO2which can’t use solar energy effectively. In research and development of catalysts, it has been paid great attention to monoclinic scheelite BiVO4as a new kind of photocatalyst. We can improve BiVO4photocatalytic activity by constructing porous structure. BiVO4with porous structure has larger specific surface area, higher electronic-hole separation efficiency, herefore, the photocatalytic activity is also improved.The concrete content of this study includes the following two parts:(1) Monoclinic BiVO4with porous structure was prepared using the hydro thermal strategy, bisumuth nitrate pentahydrate and ammonium metavanadate as materials, and P123as template. XRD showes BiVO4has excellent crystallinity, there was no obvious difference between the two patterns. DRS analysis indicated that the BiVO4and porous BiVO4haved good absorbance in the visible light region (λ≥400nm), but the absorbance intensity of porous BiVO4was bigger than that of BiVO4in λ<450nm range. SEM revealed there were many pores in porous BiVO4with polyhedron particle shape.The results of MB removal showed that surface structure and property of BiVO4was changed,also the absorption performance was improved with the intervention of the pore structure. Porous BiVO4maked photocatalytic activities better and showed outstanding photocatalytic activities for degradation of methylene blue (MB)in a unit time. The result of dynamics research shows thedegradation rate with porous BiVO4was3.05times as much as that with BiVO4. The enhanced photocatalytic performance was attributed to the enhanced absorbance ability and promoted electronic-hole separation.(2) Monoclinic BiVO4with ordered porous structures was prepared by using impregnation method, bisumuth nitrate pentahydrate and ammonium metavanadate as materials, and the KIT-6template (prepared by hydrothermal synthesis method) as template. We discussed the influnece of calcination temperature and repeating filling/conversion process on morphology and photocatalytic property of BiVO4. XPS confirmed the template of KIT-6was completely removed. WXRD, LXRD, N2sorption isotherms and TEM measurements indicated that the appropriate calcination temperature and filling/conversion time had a great influence on preparation porous BiVO4with highly efficient photocatalytic property. DRS results showed that constructing porous structure had hardly not effect on the band gap. Then the photocatalytic activities of as-prepared BiVO4were evaluated by the decolorization of rhodamine B (RhB) under visible light irradiation. The study showed that photocatalytic degradation rate of porous BiVO4was highest under400℃calcinations temperature and repeating filling/conversion two times. This enhancement could be attributed to the porous structure BiVO4prepared by appropriate calcination temperature and filling/conversion time, which promoted photoelectron from interior to the particle surface, increased the separation efficiency of photo-generated carriers.